1. Field of the Invention
The present invention relates to electrical devices that protect against overloaded circuits and, more particularly, to fused plugs for appliance cords.
2. Description of the Prior Art
The advisability of using fused plugs for household appliances is well established. In 1981, the National Fire Protection Association reported 38,520 fires resulted from appliance shorts. In 1982, there were 56,790 such fires. One reason for the above is that small appliances generally have an 18 AWG wire cord with a maximum load of 5 amp and 600 watts at 120 volts. Most house wiring is 12 AWG with a 20 amp circuit breaker. At 120 volts, the breaker won't open until 2400 watts are reached. Since this greatly exceeds the appliance cord capability, the cord will overheat and incinerate unless protected by a fuse.
Electrical plugs with built-in fuse devices have been developed as a convenient way to overcome the above-described problem. U.S. Pat. No. 2,636,096 describes a plug-in receptacle wherein a conventional tubular glass bodied fuse is incorporated into the plug circuitry. U.S. Pat. Nos. 2,988,617 and 4,275,374 utilize a similar arrangement with the same type of fuse in an insertion and ejection channel. This avoids having to dismantle the plug to replace the fuse.
The fuse ejection channel plugs have a significant problem, however, in forming a reliable connection between the fuse contacts and the plug contact parts. Axial positioning of the fuse is imprecise. Also, firm engagement of the respective contacts is often precarious, is generally weak and, at the least, creates unwanted electrical resistance.
For added convenience, a rotatable fuse assembly is shown in U.S. Pat. No. 4,196,409. When a fuse blows, a slotted hub is rotated to bring on-line a fresh fuse. Unfortunately, this device requires multiple radially extending conductors with associated fuse elements and circuitry. U.S. Pat. No. 4,309,069 also shows a rotatable fuse device comprising a conductive foil on opposing faces of a rotatable plastic body. Design objectives of each of the above devices is convenience and simplicity of use. However, the cost for such convenience is high and plug reliability is low.